Effects of Silver Doping on the Structure and Electrical Properties of γ‐CuI and the Ultraviolet Photoelectric Performance of p‐CuI/n‐Ag x Cu ₁− x I Heterojunction

Achieving the transition from p‐type to n‐type conductivity in gamma‐phase cuprous iodide (γ‐CuI) is challenging. In this work, silver (Ag)‐doped CuI films (Ag x Cu 1‐x I) were prepared by iodination method. The effects of Ag doping on the structural and electrical properties of CuI films were investigated using a combination of magnetron sputtering and solution‐phase iodination. The Ag x Cu 1 − x I films obtained by silver doping were identified as solid solutions. With increasing x , the grain size increased, the film density improved, and the optical bandgap narrowed. A transition from p‐type to n‐type conductivity was observed at x = 0.68. Based on these findings, a p‐CuI/n‐Ag 0.68 Cu 0.32 I heterojunction was fabricated. This heterojunction exhibited rectifying behavior in its dark‐state current–voltage (I–V) characteristics. Under 365 nm light illumination, the heterojunction showed a photoresponse to ultraviolet (UV) light (365 nm), with particularly high sensitivity to weak UV light (504 µW·cm − 2 ), achieving an external quantum efficiency (EQE) of 42.4%.